Consumers are becoming conscious of their diet, increasing protein intake and avoiding carbohydrates and fats. Whey proteins have branch chain amino acids responsible for muscle building. Whey protein isolate (WPI) contains more than 90% protein. The effect of incremental addition of WPI on probiotic characteristics of pure cultures and cultures in yogurt and yogurt characteristics are not known.
The hypothesis was that added WPI will influence the characteristics of yogurt culture bacteria in pure form and in yogurt. The objectives were: to determine the influence of added WPI on (1) acid and bile tolerance, growth and protease activity of pure cultures Streptococcus thermophilus ST-M5 and Lactobacillus bulgaricus LB-12, (2) growth, acid and bile tolerance of starter culture from manufactured plain yogurt, (3) the physico-chemical characteristics of yogurt over its shelf life and (4) the sensory attributes of yogurt. WPI was used at 0, 1, 2 and 3% w/v. Acid tolerance was conducted on pure cultures and cultures from manufactured plain yogurt at 30 minutes intervals for 2 hours of incubation and bile tolerance at 1 hour intervals for 5 hours. Yogurt was manufactured using 0 (control), 1, 2 and 3% WPI. For sensory evaluation, blueberry yogurt was manufactured using the same WPI concentrations. Physico-chemical analyses of yogurts were conducted every 7 days during 35 days of storage. Enumeration of yogurt cultures during yogurt´s shelf life was evaluated at 7, 21 and 35 days of storage. Sensory evaluation was conducted on yogurt 7 days after its manufacture. Data were analyzed using Proc Mixed model of SAS® 9.3 program and by analysis of variance (ANOVA) using Proc GLM. Significant differences between means were analyzed at α = 0.05 using Tukey´s adjustment. Use of 2% WPI improved acid tolerance of Streptococcus thermophilus ST-M5 in yogurt. Use of 2 and 3% WPI improved bile tolerance of Lactobacillus bulgaricus LB-12 over the 5 hours of incubation. WPI decreased syneresis of yogurts and improved sensory attributes of flavored yogurt. Overall liking scores were higher for 1% WPI yogurts compared to control. Overall, 1 or 2% WPI can be recommended in manufacture of higher whey protein yogurts.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-11152013-152635 |
| Date | 21 November 2013 |
| Creators | Vargas Lopez, Luis Alfonso |
| Contributors | Boeneke, Charles A., Aryana, Kayanush J., Xu, Zhimin |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-11152013-152635/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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